[Preoxygenation before induction for cesarean section].

In pregnant women at term, the oxygen reserve is decreased while the oxygen consumption is increased, carrying the risk of hypoxaemia during periods of apnea. Moreover, intubation of the trachea can be difficult. Therefore preoxygenation is of particular importance. The conventional method of preoxygenation consists in a 3-5 min breathing of 100% O2. However, in some obstetric emergencies, there may not be an adequate delay of time available for this technique. Recently, 4 maximally deep inspirations were demonstrated to be as effective as a 5-min inhalation of 100% O2 for preoxygenation. To determine whether these two techniques were equivalent before induction of a general anaesthesia for Caesarean section, 27 pregnant women at term (ASA 1 or 2) were studied. Following premedication with atropin sulfate (0.5 mg), the patients were randomly allocated into two groups. Group A (n = 12) was denitrogenated with 100% O2 for 4 min and group B (n = 15) with 4 maximally deep inspirations of 100% O2 within 30 s. Oxygen was administered at a flow rate of 10 L.min-1 via a non rebreathing anaesthesia system and a tight fitting face mask. Arterial saturation was assessed by pulse oximetry. General anaesthesia was induced with thiopentone (7 mg.kg-1) and succinylcholine (1.5 mg.kg-1). The trachea was intubated without previous ventilation and the delay required for the SpO2 to decrease to 93% was measured. This time was 137.9 +/- 79.2 s (extremes 85-320) in group A and 144.5 +/- 57.3 s (extremes 60-285) in group B respectively. These times were not significantly different.(ABSTRACT TRUNCATED AT 250 WORDS)